1. Field of the Invention
This invention relates to touch signal probes, and more particularly to improvements in a touch signal probe for electrically detecting contact with a workpiece to be measured.
2. Description of the Prior Art
There has heretofore been well known a three-dimensional measuring instrument for measuring the size and contour of a workpiece to be measured which is rested on measuring base board or a device for measuring a positional relationship between a tool rest and a workpiece on a machine tool. In each of the measuring devices of the type described, a touch signal probe is mounted to a movable bed movable in a desired direction with respect to the workpiece to be measured. The touch signal probe outputs an electric signal upon contact with the workpiece to be measured to cause the measuring instrument to conduct an accurate measuring action.
When the probe comes into contact with a workpiece to be measured, the touch signal probe of the type described tilts to conduct a contact-detection action. Thereafter, when released from the workpiece to be measured, the touch signal probe must be accurately returned to the original point for maintaining a highly accurate measuring. In the conventional touch signal probe, a probe to come into contact with the workpiece to be measured is tiltably and vertically movably housed and held in a probe case. When the probe comes into contact with the workpiece to be measured and vertically moved or tilted, this contact is electrically detected and a desired measuring action is conducted.
There have heretofore been proposed various types of the aforesaid probes. In each of these conventional touch signal probes, mainly the probe is biased in a predetermined direction by a means such as a spring and positioned in its static condition. However, the conventional touch signal probes have been disadvantageous in that, in order to hold the probe in a predetermined stationary position, a complicated construction is needed, working becomes troublesome, and an unstable static condition results, thus adversely affecting the measuring accuracy and so forth.
Since, in the conventional touch signal probe, the position thereof in the vertical direction and the lateral direction has been controlled by means of one and the same member and also one and the same biasing means, such disadvantages have been presented that controls of the positions in both the directions interfere with each other and so forth, and become unsatisfactory, whereby shifts in the positions occur and it becomes difficult for the probe to accurately return to the original point, thereby causing errors in the measuring and the like.
Further, in the conventional touch signal probe, there has been such a disadvantage that, if the static condition of the probe after it has returned to the original point is improved, the overstroke of the probe becomes small, so that both the static condition of the probe after returning to the original point and the overstroke cannot be improved simultaneously.
Further, the conventional touch signal probe has been disadvantageous in that the probe becomes large-sized and heavy-weighted. Because of this, there has occurred the drawback that the movable bed mounted thereto with the probe must be made touch in construction and the controllability is deteriorated.